CT abnormalities of the pancreas associated with the subsequent diagnosis of clinical stage I Pancreatic Ductal Adenocarcinoma more than one year later: a case-control study
Toshima F, Watanabe R, Inoue D, Yoneda N, Yamamoto T, Sasahira N, Sasaki T, Matsuyama M, Minehiro K, Tateishi U, Gabata T.
AJR Am J Roentgenol. 2021 Jun 23. doi: 10.2214/AJR.21.26014.
Pancreatic ductal adenocarcinoma (PDAC) is an aggressive pancreatic cancer with very poor prognosis. PDAC accounts for about 90% of primary pancreatic cancers and the 5-year overall survival is reported to be lower than 5% [1]. Surgical resection with complete tumor eradication (R0 margins) is the only curative option for patients with PDAC. However, most of patients are not candidate to surgical resection as the PDAC presents with locally advanced disease and extensive vascular infiltration, or metastatic disease. Early diagnosis of PDAC can improve the prognosis but it is often challenging in clinical practice as small lesions are commonly isodense to the background nontumoral pancreatic parenchyma on contrast-enhanced Computed Tomography (CT). Early PDAC may lack of clinical symptoms and tumor markers are not routinely adopted as screening test. The only imaging manifestations of early-stage PDAC could be the presence of secondary findings such as pancreatic ductal dilatation, glandular atrophy, and abrupt main pancreatic duct cut-off [2-4].
A recent retrospective study published by Toshima et al. [5] investigated the early findings of PDAC observed on the pre-diagnostic CT acquired at least one year before the clinical diagnosis. The authors performed a case-control study with a study group including patients with stage I PDAC who had a pre-diagnostic CT acquired at least one year before the diagnostic CT for PDAC, and a matched control group of patients without PDAC who underwent CT examination at least 10 years before the diagnostic exams [5]. Imaging analysis was performed by two radiologists who reviewed the most recent pre-diagnostic CTs in the PDAC and control groups, reporting six main focal pancreatic abnormalities: pancreatic mass, focal main pancreatic duct dilatation, focal pancreatic atrophy, focal faint parenchymal enhancement, cyst, and calcifications [5].
A total number of 103 patients with PDAC and 103 controls were included in this study [5]. When comparing the most recent pre-diagnostic CTs, patients with PDAC showed more frequently focal pancreatic abnormalities than the control group (53% vs 23%). Particularly, patients with PDAC had more commonly focal main pancreatic duct changes (13.6%), focal pancreatic atrophy (37.6%), and focal faint enhancement (26.2%) compared to controls without PDAC. A pancreatic mass was retrospectively identified in only 5% of cases on the pre-diagnostic CT in patients who developed PDAC. Interestingly, the site of focal abnormality on the pre-diagnostic CT corresponded to the site of PDAC in the diagnostic CT in 98% of patients. After the review of all pre-diagnostic CTs, focal pancreatic abnormalities were observed with higher frequencies on pre-diagnostic studies acquired 1-2 years before the PDAC diagnosis (65%), while no abnormality was observed in studies acquired with an interval time greater than 10 years before the diagnosis. Moreover, the authors observed that patients who developed PDAC demonstrated more frequently progression of these abnormalities over time compared to controls (10% vs 0%).
This study provides important information for the evaluation of focal pancreatic abnormalities that can predate the diagnosis of stage I PDAC [5]. The recognition of these focal findings could allow the early diagnosis of PDAC and improve the overall prognosis of those patients. It is important to note that the site of these findings corresponded to the site of PDAC diagnosis in 98% of cases. Moreover, temporal changes of focal abnormalities were exclusively observed in patients who developed PDAC. Therefore, a strict follow-up or further imaging assessment with MRI or endoscopic ultrasound should be considered in presence of these focal pancreatic abnormalities.
The frequency of focal abnormalities reported in this study was lower compared to some prior investigations including pre-diagnostic CTs with different interval time [6, 7]. This could be explained by the inclusion on only CTs acquired with an interval time greater than one year before the PDAC diagnosis in the study by Toshima et al. [5], while a higher frequency on pancreatic abnormalities is more likely to be observed in other studies that performed imaging closer to the clinical diagnosis [6]. Moreover, histopathological samples of these focal abnormalities has not been obtained at the time of pre-diagnostic CT due to this retrospective study design [5]. The pathophysiological changes of these abnormalities remains debated as they can be related to early tumoral changes or underlying non-tumoral conditions that can predispose to PDAC development [5].
The main limitations of this retrospective study include the lack of surgical resection in 26% patients with PDAC and the heterogeneous study protocols on pre-diagnostic CT, with lack of post-contrast imaging in 36% of patients, which limited the assessment of post-contrast focal abnormalities [5].
In conclusion, this study [5] highlight the importance of focal pancreatic abnormalities that can predate the diagnosis of PDAC. On pre-diagnostic CT obtained at least one year before the diagnosis, focal pancreatic abnormalities were present in 54% of patients and most frequently include focal parenchymal atrophy, focal faint enhancement, and focal main pancreatic duct changes. Their recognition may be helpful in clinical practice to facilitate early diagnosis of pancreatic cancer and to improve tumor resectability and patients’ prognosis.
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Dr. Roberto Cannella is a young radiologist, a PhD student in Molecular and Clinical Medicine at the University of Palermo (Italy), and an active ESGAR member regularly attending the annual meetings since 2016. During his radiology residency, Dr. Cannella spent 17 months as research scholar at the Abdominal Imaging Division of the University of Pittsburgh Medical Center (UPMC) in Pittsburgh (Pennsylvania, USA). His main research interests include diagnosis and management of focal liver lesions and preoperative assessment of pancreatic ductal adenocarcinoma, with multiple publications on these topics.
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